1. Field of Invention
The invention relates, generally, to a heat exchanger and, more particularly, to a heat exchanger used as an evaporator and a condenser.
2. Description of Related Art
FIG. 4 shows a conventional heat exchanger of “parallel flow” type, which comprises a first header 1′, a second header 2′, a plurality of tubes 3′, a plurality of fins 4′, a first connection pipe 5′, and a second connection pipe 6′. The first connection pipe 5′ is welded to the proximal end of the first header 1′, and the second connection pipe 6′ is welded to the proximal end of the second header 2′. A plurality of tubes 3′ are connected between the first and second headers 1′, 2′, and, as shown in FIG. 5, two ends of each tube 3′ are partially extended into the first and second headers 1′ and 2′, respectively.
When the heat exchanger is used as an evaporator, the first header 1′ is used as an inlet header and the second header 2′ is used as an outlet header. A mixture of liquid and vapor refrigerant enters the first header 1′ from the first connection pipe 5′ along solid-line arrow “A′,” then becomes vapor refrigerant after exchanging heat with the external environment during passage through the plurality of tubes 3′, and is finally discharged out of the heat exchanger via the second connection pipe 6′.
When the heat exchanger is used as a condenser, the second header 2′ is used as an inlet header, and the first header 1′ is used as an outlet header. Vapor refrigerant enters into the second header 2′ from the second connection pipe 6′ along dashed-line arrow “B′,” then becomes liquid refrigerant after exchanging heat with the external environment during passage through the plurality of tubes 3′, and is finally discharged out of the heat exchanger via the first connection pipe 5′.
Since two ends of each tube 3′ are partially extended into the first and second headers 1′ and 2′, respectively, the refrigerant in the first header 1′ or second header 2′, which is used as an inlet header, may be disturbed or influenced disadvantageously by the portions of the plurality of tubes 3′ extended into the inlet header, and separation of vapor refrigerant and liquid refrigerant in the two-phase flow may occur. In addition, the distribution of the refrigerant in the first header 1′ or second header 2′ is not uniform so that the amount of the refrigerant distributed in each of the plurality of tubes 3′ is not uniform, which may result in inefficient heat transfer.
Further, as shown in FIG. 5, since two ends of each tube 3′ are partially extended into the first and second headers 1′ and 2′, respectively, when the first header 1′ or second header 2′ is used as an outlet header, the flow of the refrigerant in the outlet header may be disturbed disadvantageously by the portions of the plurality of tubes 3′ extended into the outlet header, thus causing spiral vortexes. And, the flow resistance is large especially in the outlet header used as the evaporator. In addition, the vapor refrigerant is especially affected disadvantageously by the portions of the plurality of tubes 3′ extended into the outlet header, and more spiral vortexes will be generated. In order to balance the flow resistance, the flow rate in the plurality of tubes 3′ at the distal end of the header is much smaller than that in the plurality of tubes 3′ at the proximal end of the header, thus causing the refrigerant distribution in the plurality of tubes 3′ to be non-uniform, which can result in inefficient heat transfer. At the same time, the large flow resistance in the heat exchanger will result in inefficient heat transfer of the refrigeration system employing the heat exchanger.
In addition, the first and second connection pipes 5′, 6′ are welded directly to the proximal ends of the first and second headers 1′, 2′, respectively, so that the replacement and maintenance are not convenient, thus disadvantageously affecting the convenience of use.
Thus, there is a need in the related art for improvement of heat-transfer performance of a heat exchanger. More specifically, there is a need in the related art for improvement of uniform distribution of the refrigerant. Also, there is a need in the related art for non-disturbance of flow of the refrigerant. And, there is a need in the related art for improvement of heat-transfer efficiency. Furthermore, there is a need in the related art for facilitation of replacement and maintenance. In addition, there is a need in the related art for satisfaction of requirements of different types of heat exchangers used in different applications. Moreover, there is a need in the related art for effective removal regularly. Plus, there is a need in the related art for extension of service life of the heat exchanger. There is a need in the related art for effective adjustment of distribution of the refrigerant as well.